GB2330366A - Sump member for catch-pit structure - Google Patents

Abstract

A sump member 10 is moulded from glass-fibre reinforced plastic. Its floor has apertures for ingress of water where the water table is high. The end wall 14 has a pipe-connection aperture 16. Four concrete rings 18 are stacked on the sump member 10. The rings 18 are rectangular and interfit by tabs 20 and notches 22. To construct a catch-pit, a sump member 10 is placed in the bottom of a hole or other excavation. Any necessary connections to the pipe-connection apertures 16 are made. The sump member can then be backfilled with ballast or rubble, as appropriate. A first concrete ring 18 is placed in the top of the sump member so that it is supported on the ledge 24. This ring provides strength and rigidity. Further rings 18 are then stacked on first ring and secured together by their tabs 20 and notches 22. This is continued until the desired height has been reached. Back filling of the hole can then be completed and the catch-pit structure fitted with a cover or lid. The whole construction operation can be carried out from ground level. The need for shuttering is avoided.

Description

CATCH-PITS This invention relates to catch-pits, for example those forming part of railway drainage schemes.

It is known to construct a catch-pit forming part of a railway drainage scheme by digging a hole of suitable depth in the ground and then building the catch-pit from concrete components. These typically include three concrete slabs which are laid in the bottom of the hole to form a floor of the catch-pit. The walls of the catch-pit are then formed by stacking concrete rings of rectangular shape on one another until the structure reaches ground level. These rings are typically 1270mm by 735mm in plan and 115mm deep and interfit by way of protruding tabs formed in the upper surfaces of the rings and corresponding notches in the lower surfaces.

Typically, each longer side has two notches and two tabs and each shorter side one of each. Pipe-connection apertures can be formed by using a pair of "half" rings of U-shape or Cshape in plan but having their free limbs shorter than onehalf the length of the corresponding side of the "full" rings.

The pipe-connection apertures are typically formed close to the floor of the structure but spaced upwardly therefrom by two or three "full" rings. A sump is thereby formed in the catch-pit beneath the level of the apertures.

Construction of a catch-pit as described is labourious and time-consuming. It is also necessary for personnel to climb into the hole in order to build the catch pit. This is a particular problem under recent new legislation which requires shuttering to be erected within the hole if the hole is greater than 1.2m in depth and personnel are to work in the hole.

GB-A-2150953 describes a catch-pit which is constructed entirely from modular components of plastics material, specifically unplasticised polyvinyl chloride or high density polyethylene. The sump and connection pan module has a circular floor formed from sheet material which is joined by hot-air welding to a tubular wall in which then are four circular pipe-connection apertures spaced upwardly from the floor. The floor is apertured to allow ingress of water at locations where the water table is high.

The object of the present invention is to simplify the construction of catch-pit structures of the kind first described.

The invention provides a sump member for a catch-pit structure, the sump member being formed in one piece of plastics material and having a floor, wall means extending upwardly from the floor and, adjacent the upper edge of the walls, ledge means for receiving a concrete ring member which, when received, fits snugly within the upper part of the wall means to provide a base to support a stack of further ring members forming a catch-pit structure.

A structure can be built according to the invention by personnel working at ground level lowering the component parts into the hole. The need to provide shuttering is thus avoided.

The plastics material is preferably glass-fibre reinforced plastic ("GRP").

The floor may be apertured to allow ingress of water; the wall means may have one or more pipe-connection apertures therein.

Conveniently, the ledge means comprises a continuous internal shoulder extending around the wall means.

The ledge means is typically from 90 to 115 mm below the top edge of the wall means and, independently thereof, from 70 to 105 or 115 mm wide.

Advantageously, the ledge means is shaped and dimensioned also to receive a member which extends across the interior of the sump member to provide a support surface (a so-called "rodding ledge") on which a workman can stand whilst working in the catch pit structure.

The invention also provides a method of construction of a catch-pit structure, in which a sump member as referred to above is placed in at the bottom of a hole in which the catchpit is to be constructed, a first concrete ring is placed in the upper part of the sump member received on the ledge means, to fit snugly within the upper part of the wall means of the sump member, and further concrete rings are stacked on the first ring in order to form the catch-pit structure.

Afterwards, the structure can be back-filled with ballast or other suitable material.

The present invention provides for a much more convenient catch-pit construction in terms of time and labour involved than the first structure described using entirely concrete components. It should be noted that the sump and connection pan module described in GB-A-2150953 would be entirely unsuitable for the purpose to which the sump member of the present invention is put since that sump module lacks entirely the ledge means for supporting the concrete ring and would generally be of insufficient strength to support any subsequent rings.

The invention will now be described further by way of example with reference to the embodiments shown in the drawings in which: Figure 1 shows a catch-pit sump member of the invention, on which four conventional concrete rings are stacked; Figure 2 shows the uppermost part of the sump member of Figure 1, without the rings; and Figure 3 is a view corresponding to Figure 2 of a modified sump member having a rodding ledge.

Figure 1 shows a catch-pit sump member 10 which is moulded in one piece from glass-fibre reinforced plastic. The sump member 10 is rectangular in plan and has side and end walls 12, 14 which slope slightly outwardly away from a rectangular floor (not visible).

The internal dimensions at the top of the walls 14, 16 are 1272mm by 740mm. The sump member is 650mm deep but other depths, for example in the range 540mm to 980mm are also possible. The sump member floor has a number of apertures for ingress of water at locations where the water table is high.

The end wall 14 has a pipe-connection aperture 16. Similar apertures could be provided in other walls. For certain applications, two holes one above the other can be provided for example for connection of a carrier and a collector pipe in areas of high water table.

Four conventional concrete rings 18 are stacked on the sump member 10. The rings 18 are rectangle in plan and are each 1270mm long, 735mm wide and 115mm deep. The rings interfit by way of protruding tabs 20 and corresponding notches 22. Each side and end of each ring is itself approximately square in cross-section.

Figure 2 shows the upper part of the sump member 10 with the rings 18 removed. The sump member is formed with a continuous internal ledge 24 which is about 80mm wide and about lOOmm below the top edge of the side and end walls 12,14. The upper part of the walls 12,14 is thus dimensioned to receive the lowermost ring 18 snugly and support the ring on the ledge 24. The ring 18 thus reinforces and strengthens the-upper part of the sump member 10.

In the modification of Figure 3, the ledge 26 is steppeddown along one side of the sump member and along an adjacent end portion of each end of the sump member. This allows a rodding ledge 28 to be fitted in the sump member before the concrete rings 18 shown in Figure 1. One side and each end of the upper surface of the rodding ledge then provides support for the lowermost ring 18. The rodding ledge is formed from concrete and thereby provides a permanent support for a workman climbing into the structure to carry out a rodding or other operation.

To construct a catch-pit using the components described, a sump member 10 as shown in Figure 1 or Figure 3 is placed in the bottom of a suitably prepared hole or other excavation.

Any necessary connections to the pipe-connection apertures 16 are made at this stage. If appropriate a rodding ledge 28 is fitted. The sump member can then be backfilled with ballast or rubble, as appropriate. A first concrete ring 18 is then placed in the top of the sump member so that it is supported on the ledge 24 or on the ledge 24 and the upper surface of the rodding ledge 28. This ring provides strength and rigidity for the upper part of the sump member. Further rings 18 are then stacked on first ring and second together by means of their tabs 20 and notches 22. This is continued until the desired height has been reached. Back filling of the hole can then be completed and the catch-pit structure fitted with a suitable cover or lid. The whole construction operation can be carried out from ground level. The need for shuttering is thereby avoided.

Claims (10)

1. A sump member for a catch-pit structure, the sump member being formed in one piece of plastics material and having a floor, wall means extending upwardly from the floor and, adjacent the upper edge of the walls, ledge means for receiving a concrete ring member which, when received, fits snugly within the upper part of the wall means to provide a base to support a stack of further ring members forming a catch-pit structure.

2. A sump member according to claim 1, in which the ledge means comprises a continuous internal shoulder extending around the wall means.

3. A sump member according to claim 1 or 2, in which the ledge means is shaped and dimensioned also to receive a member which extends across the interior of the sump member to provide a support surface on which a workman can stand whilst working in the catch pit structure.

4. A sump member according to any preceding claim, in which the floor is apertured to allow ingress of water.

5. A sump member according to any preceding claim, in which the wall means have one or more pipe-connection apertures therein.

6. A sump member according to any preceding claim, in which the plastics material is glass-fibre reinforced plastic.

7. A method of construction of a catch-pit structure, in which a sump member according to any preceding claim is placed in at the bottom of a hole in which the catch-pit is to be constructed, a first concrete ring is placed in the upper part of the sump member received on the ledge means, to fit snugly within the upper part of the wall means of the sump member, and further concrete rings are stacked on the first ring in order to form the catch-pit structure.

8. A method according to claim 7, in which the catchpit structure is subsequently back-filled with ballast or other suitable material.

9. A sump member for a catch-pit structure, substantially as hereinbefore described with reference to the drawings.

10. A method of construction of a catch-pit structure, substantially as hereinbefore described with reference to the drawings